Axial alignment mechanisms are employed in on-vehicle disk brake lathes to connect between a spindle of the lathe and a hub adapter that mounts to a wheel hub on which a brake disk to be machined is also mounted. The alignment mechanism is adjustable in order to substantially align a spindle axis, which is the axis about which the lathe spindle rotates, with a hub axis, about which the wheel hub and brake disk rotate. Substantially aligning the spindle axis with the hub axis avoids introducing lateral runout in the brake disk when its surfaces are machined in a direction normal to the spindle axis. One mechanism that is well-suited for use with an automatic alignment system uses a pair of opposed slant disks to adjust the magnitude and orientation of the angle of misalignment to compensate for misalignment in the elements interposed between the spindle and the wheel hub. Such an alignment mechanism 10 is shown in FIGS. 1 and 2, adjusting the alignment of a lathe spindle 12 and a hub adapter 14 (shown in FIG. 2) to substantially align a spindle axis 16, about which the lathe spindle 12 rotates, with a hub axis 18, about which the hub adapter 14 rotates.
The alignment mechanism 10 has a base 20 for affixing to the lathe spindle 12 and a cap 22 for mounting against the hub adapter 14, and the adjustment is made by varying the positions of a first slant disk 24 and a second slant disk 26 that are interposed between the base 20 and the cap 22 and which each have side surfaces that are inclined with respect to each other. A torque transfer post 28 extending from the base 20 engages a post recess (not shown) on the cap 22 to prevent rotation therebetween; this allows the base 20, which is driven by the lathe spindle 12, to in turn drive rotation of the cap 22, while allowing a limited degree of non-rotational motion to accommodate the adjustment of the alignment. The cap 22 in turn has a pair of lug recesses 30, one of which is engaged by a lug 32 on the hub adapter 14 to allow the cap 22 to drive rotation of the wheel hub to which the hub adapter 14 is attached.
Ring bearings are interposed between the elements to allow independent rotation of the two slant disks (24 and 26). A base ring bearing 34 is interposed between the base 20 and the first slant disk 24, a central ring bearing 36 is interposed between the first slant disk 24 and the second slant disk 26, and a cap ring bearing 38 is interposed between the second slant disk 26 and the cap 22. The ring bearings (34, 36, 38) and the slant disks (24, 26) are maintained in axial alignment by a centering cylinder 40 provided on the base 20.
To retain the elements of the alignment mechanism 10 together, a retention ring 42 is provided, which attaches to a sleeve 44 extending from the base 20 and forcibly engages the cap 22 via a wave spring 46. The wave spring 46 applies pressure to maintain the base 20, the ring bearings (34, 36, 38), the slant disks (24, 26), and the cap (22) in contact and assures that they remain in proper position relative to each other.
When the alignment mechanism 10 is in service, a drawbar assembly 48 (only partially shown) engages the hub adapter 14 and the lathe spindle 12 and operates to force the hub adapter 14 toward the lathe spindle 12, thereby forcibly engaging together the base 20, the ring bearings (34, 36, 38), the slant disks (24, 26), and the cap (22). The ring bearings (34, 36, 38) allow the slant disks (24, 26) to be rotated even when the elements are forcibly engaged together.
The first slant disk 24 and the second slant disk 26 are individually driven by an alignment adjustment system that allows the driven slant disk (24 or 26) to be incrementally moved with respect to the base 20 and the cap 22. If the non-driven slant disk (26 or 24) does not track the motion of the driven disk (24 or 26), this incremental motion serves to adjust the magnitude of the angle of misalignment between the spindle axis 16 and the hub axis 18 and to adjust the orientation of this angle about the spindle axis 16. Such adjustment of alignment using slant disks is taught in U.S. Pat. No. 6,101,911, and is typically done incrementally in a trial-and-error method, with each adjustment evaluated as to whether it increases or decreases the misalignment, and further adjustments being made accordingly.
The alignment adjustment system for use with the alignment mechanism 10 employs a series of spur gears 50 that are each rotatably mounted with respect to the base 20 and configured to engage peripheral teeth 52 on one of the slant disks (24, 26), as shown in FIGS. 1 and 2, to drive the slant disks (24, 26) of the alignment mechanism 10. Each of the spur gears 50 is operably connected to a star wheel 54 such that rotation of the star wheel 54 causes rotation of the spur gear 50 operatively connected thereto, and in turn rotation of the slant disk (24, 26) engaged by the spur gear 50 either in a first direction, when the spur gear 50 is directly connected to the associated star wheel 54 so as to rotate therewith, or in a second and opposite direction when the spur gear 50 is connected to the associated star wheel 54 through an idler gear 56 so as to rotate in a direction opposite that of the star wheel 54. The alignment adjustment system employs a solenoid (not shown) such as described in the '911 patent to selectively rotate the star wheels 54 in one direction to adjust the alignment.
While the ring bearings (34, 36, 38) allow each of the slant disks (24, 26) to be driven independently, independent rotation does not necessarily follow. Coupling of the rotation of the two slant disks (24, 26) has been found to occur, since the compression forces on the stacked elements provided by the drawbar assembly 48 result in frictional forces associated with the central ring bearing 36. As a result of these frictional forces, as one slant disk (24 or 26) is rotated, torque is transmitted through the central ring bearing 36 to the other slant disk (26 or 24), causing it to rotate as well. Such rotation of the other slant disk impairs the ability to individually rotate each of the slant disks (24, 26) to make adjustments in their relative positions. To reduce such coupling of the rotation, a drag force is applied to the slant disk gears by friction disks 58 interposed between each of the star wheels 54 and the base 20. These friction disks 58 become compressed when the star wheel 54 is mounted to the base 20, and the compression causes a frictional resistance to rotating the star wheel 54. While such has been found effective, the drag on the star wheels 54 requires the alignment adjustment system to apply a greater force to rotate the star wheels 54 when making adjustments in the alignment, and thus requires a greater size and weight of the alignment adjustment system. The greater force needed also accelerates wear on the star wheels.